Automatic sample testing machine

ABSTRACT

An automatic sample testing machine for testing samples stored in test cards. The machine has a test sample positioning system for moving a tray containing a plurality of test sample cards and fluid receptacles among various stations in the machine. The machine has a diluting station for adding a predetermined quantity of diluent to the receptacles as needed. A pipetting station transfers fluid from one receptacle to another. A vacuum station is provided having a vacuum chamber moveable relative to the tray between upper and lower positions. The chamber cooperates with the tray to make a sealing engagement with the top surface of the tray when it is lowered to the lower position. A vacuum generator supplies vacuum to the chamber. When the vacuum is released from the chamber, the fluid samples are loaded into the cards from the receptacles. The test sample positioning system moves the tray to a cutting and sealing station and then to an incubation station and loads the cards one at a time into a carousel within the incubation station. A test card transport station transports the test cards from the incubation station to an optical reading station, where optical measurements (e.g., transmittance and/or fluorescence optical testing) is conducted on the wells of the card. When the card has been read, it is either moved back to the incubation station for additional incubation and reading or transferred to a card disposal system when the reading is complete.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 09/006,623 filed Jan. 13,1998, now U.S. Pat. No. 5,965,090, which is a divisional of applicationSer. No. 08/604,672 filed Feb. 21, 1996, now U.S. Pat. No. 5,762,873.

BACKGROUND OF THE INVENTION

A. Field of the Invention

This invention relates to machines and systems for automatically loadinga test sample card having one or more reagent filled sample wells withfluid samples (e.g., samples containing microbiological agents), and forconducting optical analysis of the samples after reaction with thereagents. The invention is particularly suitable for use in biological,blood or chemical analysis machines, as well as immunochemistry andnucleic acid probe assay machines.

B. Description of Related Art

Biological samples can be reacted and subjected to chemical or opticalanalysis using various techniques, including transmittance and/orfluorescence optical analysis. The purpose of the analysis may be toidentify an unknown biological agent or target in the sample, todetermine the concentration of a substance in the sample, or determinewhether the biological agent is susceptible to certain antibiotics, aswell as the concentration of antibiotics that would be effective intreating an infection caused by the agent.

A technique has been developed for conducting optical analysis ofbiological samples that involves the use of a sealed test sample cardcontaining a plurality of small sample wells. Typically, duringmanufacture of the cards, e.g. for microbiological analysis, the wellsare filled with either various types of growth media, for variousbiological agents, or else various concentrations of differentantibiotics. The cards have an internal fluid passageway structure forallowing fluid to enter the wells of the card through a transfer tubeport. An L-shaped integral transfer tube extends outwardly from thetransfer tube port. The prior art method involved the manual insertionof one end of the transfer tube into the card and the other end into atest tube, and then the manual placement of the card with attachedtransfer tube and test tube into a vacuum filling sealing machine, suchas the Vitek® Filler Sealer. The filling and sealing machine generates avacuum, causing the fluid in the test tube to be drawn into the wells ofthe sample card.

After the wells of the card are loaded with the sample, the cards aremanually inserted into a slot in a sealer module in the machine, wherethe transfer tube is cut and melted, sealing the interior of the card.The cards are then manually removed from the filler/sealer module andloaded into a reading and incubating machine, such as the VITEK® Reader.The reading and incubating machine incubates the cards at a desiredtemperature. An optical reader is provided for conducting transmittancetesting of the wells of the card. Basically, the cards are stacked incolumns in the reading machine, and an optical system moves up and downthe column of cards, pulling the cards into the transmittance optics oneat a time, reading the cards, and placing the cards back in the columnof cards. The VITEK® reading machine is described generally in theCharles et al. patent, U.S. No. 4,188,280.

This arrangement has limitations, in that two machines, a filler/sealerand a reader, are required to process and analyze the cards.Furthermore, additional time and labor are required to conduct thecomplete analysis of the card.

Combining the several functions of biological sample processing andoptical reading into a single automatic sample processing and readingmachine poses substantial challenges. One particularly difficultchallenge is to provide a way of conducting the vacuum loading of thecards, and to provide a way for moving the loaded sample card toincubation and optical reading stations. Another challenge is to designa transport system for moving the sample cards and receptacles about themachine to the various stations.

The present inventive automated sample testing machine achieves thesegoals by providing a machine that performs dilutions for susceptibilitytesting, fills the cards with the samples at a vacuum station, and sealsthe card by cutting the transfer tube, and conducts incubation andoptical transmittance and fluorescence analysis of the cards, allautomatically. The machine is capable of conducting simultaneoussusceptibility and identification testing of a sample placed in a singletest tube. The machine provides for rapid, automatic identification andsusceptibility testing of the sample. In a preferred form of theinvention, a number of different test samples are tested simultaneously,and moved in a sample tray or "boat" around the machine among thevarious stations. The tray receives, a cassette that contains aplurality of test tubes and associated test sample cards. The machineprovides for novel pipetting and diluting stations, permitting fluids tobe added to the test tubes or transferred from one test tube to another.

The machine further has a unique test sample positioning system thatmoves the tray (with test tubes and cards) about the machine over a basepan. The design of the positioning system is such that it permitsessentially a custom configuration of stations above the base pan.Expansion of the machine to include additional carousels and readingstations, or addition types in intermediate procession stations such asdilution stations or vacuum stations, can be readily accomplished.

These and still other features of the invention will be come moreapparent from the following detailed description of a presentlypreferred embodiment of the invention.

SUMMARY OF THE INVENTION

A machine is provided for automatically testing a fluid sample deliveredto reagent-filled wells of a test sample card. The machine has a loadingstation and a sample tray moveable within the machine from the loadingstation to various stations, where operations are performed on the testsample and the test sample card. The samples are placed in fluidcommunication with the test sample cards when the samples and cards areloaded into the tray.

The machine includes a vacuum station having a vacuum chamber moveablerelative to the tray between upper and lower positions. When the vacuumchamber is lowered to its lower position, the vacuum chamber cooperateswith a peripheral horizontal surface in the tray to make a sealingengagement with the tray. The vacuum station has a vacuum source forsupplying vacuum to the chamber and valves for controlling the drawingof vacuum and releasing the vacuum. The fluid samples are loaded in thecards when the vacuum is released from the vacuum chamber.

In one aspect of the invention, novel vacuum loading techniques areprovided for the vacuum station in order to prevent air bubbles fromentering the wells of the card. These techniques include maintaining apredetermined rate of change of pressure in the vacuum pressure asvacuum in drawn, and maintaining the vacuum level at a threshold or setpoint for a short period of time in order to properly fill the card.After the vacuum loading process is completed, the tray is then advancedto a sealing station, where a hot cutting wire is used to cut off thetransfer tube for the card and seal the interior of the card from theatmosphere.

The machine also has an incubation station for incubating the card. Atest sample positioning system is provided for moving the tray from theloading station to the vacuum station and from the vacuum station to theincubation station. An optical reading station is provided for readingthe cards during incubation of the cards in the incubation station. Atest sample card transport station is provided for transporting the testsample card from the incubation station to the optical reading stationwhere the optical reading station conducts optical analysis of thesample loaded into the test sample card.

In a preferred form of the invention, a diluting station is provided forselectively adding diluent to the receptacles or test tubes in the tray.A pipetting station is also provided for transferring fluid samples fromone receptacle to another. The diluting and pipetting stations arepreferably placed close to each other, so as to permit simultaneouspipetting and diluting operations to be performed on the receptacles inthe tray.

In another aspect of the invention, the sample cards and receptacles areloaded onto a cassette, and the cassette placed in the tray in themachine. A stand-alone information system is provided for associatingfluid or test sample and test card information with the cassette. Amachine-readable memory storage device is applied to the cassette. Amachine-readable indicator is applied to the sample cards and isidentified with each of said test sample cards. An information loadingstation reads the machine-readable indicators for a plurality of thesample cards when they are loaded in the cassette, and storesinformation regarding said test sample cards onto the machine-readablememory storage device. As the cassette is moved within the automatedsample testing machine, it passes by an information retrieving stationwhich retrieves information stored in said machine-readable memorystorage device.

In a preferred embodiment, the information loading station has a memory,a human interface for transferring testing information input from a userof the system into the memory, a reader for the machine readableindicator, and a software program responsive to the human interface forassociating in the memory testing information from the user with themachine-readable indicator applied to the test sample card.

BRIEF DESCRIPTION OF THE DRAWINGS

Presently preferred embodiments of the invention are depicted in thedrawings, wherein like reference numerals refer to like elements in thevarious views, and wherein:

FIG. 1 is a perspective view of a preferred automatic biological sampletesting machine in accordance with the invention. The card disposalstation is removed in order to more clearly show the other features ofthe machine.

FIG. 1A is a block diagram of the all of the principal stations in themachine of FIG. 1.

FIG. 2 is a perspective view of the machine of FIG. 1, with the dilutingand pipetting stations removed to better illustrate the vacuum stationof the machine, and with the stacking disposal station added.

FIG. 3 is an end view of the machine, partially in section, as seen fromthe right-hand side of the machine looking toward the center mount.

FIG. 4 is a detailed view of the vacuum chamber of the vacuum station ofFIG. 2 engaging the top surface of the boat, as it would be when thefluid samples are loaded into the cards.

FIG. 5 is a detailed view of the cut and seal station, showing the hotcutting wire cutting through the transfer tubes for the cards when theboat is advanced past the hot cutting wire, thereby sealing the interiorof the cards.

FIG. 6 is a detailed perspective view of the test sample positioningsystem of FIGS. 1 and 2.

FIG. 7 is a plan view of the base pan of FIG. 6.

FIG. 8 is a more detailed perspective view of the diluting and pipettingstations of FIG. 1.

FIG. 9 is an elevational view of the diluting and pipetting stations ofFIG. 8.

FIG. 10 is a side view of the diluting station of FIG. 9.

FIG. 11 is a perspective view of the pipetting hopper system of FIGS. 1and 9 when the pipette housing is rotated to a pipetting fill position,with the cover swung open to permit the housing to be filled withpipettes.

FIG. 12 is an end view of the pipetting hopper system showing themovement of a horizontal slide between two positions, controlling theability of pipettes to be removed from the housing via a slot in thehousing.

FIG. 13 is an exploded view of the pipette hopper system of FIGS. 10 and11.

FIG. 14 is an elevational view of the pipetting station 300 of FIG. 1,with the tubular tapered transfer pin assembly rotated to a fluidwithdrawal position where the straw can be lowered into a receptacle.

FIG. 15 is a side view of the tubular tapered transfer pin assembly asseen from the straw hopper of FIG. 14.

FIG. 16 is a top plan view of the tubular tapered transfer pin assemblyalong the lines 16--16 of FIG. 15;

FIG. 17 is a plan view of a preferred sample card transport system forthe machine of FIGS. 1 and 2.

FIG. 18 is a sectional view of the carriage and slide assembly of FIGS.17, which permits the drive subassembly to move relative to thebulkhead.

FIG. 19 is a side view of the sample card transport station of FIG. 17,looking in the direction of the carousel and incubation station of FIGS.1 and 2.

FIG. 20 is a perspective view of the fluorescence optical substation ofthe optical reading system of FIGS. 1 and 2, with the reflector assemblyin an open position to better illustrate the optical head and theoptical shuttle.

FIG. 21 is a sectional view of the fluorescence optical substation ofFIG. 20.

FIG. 22 is a detailed elevational view of the transmittance substationof FIG. 3.

FIG. 23 is a perspective view of one of the LED transmittance sources ofFIG. 22.

FIG. 24 is a sectional view of one of the transmittance sources of FIG.22, showing the relationship between the LED transmittance light source,sample well, and photodiode detector.

FIG. 25 is an elevational view of the sample well and LED output for thetransmittance substation of FIG. 22.

FIG. 26 is a perspective view of a stand-alone data input station thatloads information from bar codes placed across the top of the cards 28onto a pair of touch memory buttons.

FIG. 27 is a illustration of a portion of the center mount and base panof FIG. 1, showing the placement of a touch memory button readingstation along the side of the center mount. The two contacts of thereading station touching the two touch memory buttons on the side of thecassette as the boat and cassette are moved past the station.

FIG. 28 is a side view of a portion of the cards and cassette as itpasses by the bar code reading station;

FIG. 29 is a schematic diagram of the vacuum station of FIG. 3; and

FIG. 30 is a graph of showing the change in vacuum inside the vacuumchamber of FIG. 29 as a function of time during the loading of thecards.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Overview of PreferredAutomatic Sample Testing Machine

FIG. 1 is a perspective view of a biological sample testing machine 20that conducts analysis of test sample filled cards 28 according to apreferred embodiment of the invention. In FIG. 1, a stacking carddisposal station for the cards 28 has been removed in order toillustrate the other components of the machine. The card disposalstation 900 is shown in FIG. 2. FIG. 3 is an end view of the machine,partially in section, showing the position of the test sample cards 28as they are processed in several of the stations in the machine 20. FIG.1A is a block diagram of the machine 20 as whole, showing the layout ofthe stations and the path of the boat and cassette and test sample cardsthrough the machine in a preferred embodiment of the invention.

Referring now primarily to FIGS. 1, 1A and 3, the biological sampletesting machine 20 includes a biological test sample positioning system100, consisting of four independent motor-driven paddles, which isdesigned to pull a sample tray 22 (referred to herein as a "boat")incorporating a cassette 26 across a base pan 24 around the machine 20to several discrete stations, where various operations are performed onthe cards and receptacles in the cassette 26. Prior to the start of theprocedure, a technician loads a cassette 26 with a plurality of testcards 28 and receptacles such as test tubes 30 containing biological orcontrol samples to be tested. Each test card 28 has an L-shaped transfertube 32 protruding therefrom for permitting the fluids containingbiological samples to be drawn from the test tubes 30 into thereagent-filled wells of the test cards 28. The technician places theloaded cassette 26 into the boat 22 at a loading station for themachine, such as the front, right hand corner of the base pan 24 shownin FIG. 1. The combined boat 22 and loaded cassette 26 are then moved asa unit over the surface of the base pan 24 about the machine 20 by thetest sample positioning system 100.

In a typical microbiological testing scenario, described below forpurposes of illustration but not limitation, the test cards 28 come intwo varieties: (1) identification cards, in which particular differentgrowth media are placed in each of the wells of the card 28 when thecards are manufactured, and (2) susceptibility cards, in which differentconcentrations of different antibiotics are placed in each of the wellsof the card 28. The identification cards are used to identify theparticular unknown biological agent, i.e., microorganism, present in thesample. The susceptibility cards are used to determine thesusceptibility of the biological agent to various concentrations ofantibiotics or other drugs. In the test procedure described below,identification and susceptibility tests can be performed on a singlesample in one cycle of operation of the machine 20. To accomplish this,the cassette 26 is loaded such that a test tube 30A containing abiological sample, connected via a transfer tube 32 to an identificationcard 28A, is placed adjacent to a test tube 30B connected via a transfertube 32 to a susceptibility card 28B.

The cards 28 preferably contain bar codes as well as other identifyingindicia on the card for reading by a bar code reader built into themachine 20. The bar codes are unique to each card, and identify cardinformation such as card type, expiration date, and serial number, andare used to correlate test data and/or results from the cards with thepatient and the biological sample. In addition, the entire boat orcassette may have sample information for all of the cards loaded in thecassette stored on one or more memory devices affixed to the cassette26, such as a memory button or "touch button" available from DallasSemiconductor Corp., 4401 S. Beltwood Parkway, Dallas, Tex.

In the representative example shown in FIG. 1, seven or eight of thetest tubes 30 in the boat 22 contain biological samples, and are influid communication with identification cards 28A by the straw-liketransfer tube 32. The biological sample test tube 30A and its associatedidentification card 28A can be thought of as a set. The biologicalsample test tubes and identification cards are typically arranged in analternating pattern in the cassette 26. Each biological sample test tube30A and identification card 28A set is adjacent to an empty test tube30B placed in communication with a susceptibility card 28B via atransfer tube 32. It will be appreciated that the cards and associatedtest tubes could be ordered in any order in the cassette 26 depending onthe particular testing requirements for the samples. For example, thecards could be arranged as follows: identification (ID), susceptibility(SU), ID, ID, ID, SU, SU, ID, SU . . . . Further examples would be allidentification cards and all susceptibility cards.

The test sample positioning system 100 operates to move the boat 22 andcassette 26 over the base pan 24 first to a diluting station 200. Thediluting station contains a rotating shot tube 202, by which apredetermined volume of diluent (such as saline solution) is added tothe empty susceptibility test tubes in the cassette 26, e.g. test tube30B. As the leading edge of the boat 22 is moved to the left during thisprocess, it passes under a pipetting station 300. The pipetting station300 includes a mechanism that automatically removes a pipette 302 from asource of pipettes 304, lowers the pipette 302 into the biologicalsample test tube 30A, and removes with vacuum a predetermined volume ofbiological fluid from the biological sample test tube 30A using thepipette 302.

The test sample positioning system 100 then moves the boat 22 to theleft by an amount equal to the separation distance between adjacent testtubes 30A and 30B, e.g. 15 mm. The pipetting station 300 then lowers thepipette 302 containing the biological fluid from the biological sampletest tube 30A into the adjacent susceptibility test tube 30B (havingalready received a quantity of diluent from the diluting station 200),expels the fluid into the test tube 30B, and drops the pipette 302 intothe susceptibility test tube 30B. The process of movement of the boat 22by the test sample positioning system 100, adding diluent to thesusceptibility test tubes 30B at the diluting station 200, andtransferring of biological samples from the biological sample test tubes30A to the adjacent susceptibility test tubes 30B at the pipettingstation 300, continues until all of the identification and/orsusceptibility test tubes sets (if any) in the boat 22 have been soprocessed. By virtue of the close spacing of the pipetting station 300and the diluting station 200, simultaneous diluting and pipettingoperations can be performed on multiple test tubes in a single boat 22.After the last pipetting operation has been performed, the test samplepositioning system 100 then moves the boat 22 all the way to theleft-hand edge of the base pan 24.

It will be understood by persons skilled in the art that the cassette 26may be loaded entirely with biological samples in the test tubes 30 andidentification card 28, such as the case where a batch of biologicalsamples are to be tested to identify the contents of the samples. Inthis example, the diluting and pipetting operations are not necessary.However, in other types of sample testing, other diluents or fluids maybe added to or withdrawn from the test tubes. In the example of where nodiluting or pipetting operations are performed (e.g., where thepipetting and diluting operations were performed off-line), the cassette26 is loaded with test tubes and cards, and the positioning system 100would simply move the boat 22 and loaded cassette 26 directly past thediluting station 200 and the pipetting station 300 without stopping, allthe way to the left hand edge of the base pan 24.

Once at the left hand edge of the base pan 24, the test samplepositioning system 100 operates to move the boat 22 along the left handedge to a vacuum station 400. The vacuum station 400 is seen better inFIG. 2, which is a perspective view of the machine 20 with the dilutingstation 200 and the pipetting station 300 removed, and in FIGS. 4 and 5.At the vacuum station 400, a vacuum chamber 402 is lowered onto the boat22 such that the bottom surface of the vacuum chamber 402 sealinglyengages the top peripheral surface 23 of the boat 22. The vacuum chamberhas hoses 406, 408 (FIG. 4) that are in communication with aconventional vacuum source for the machine (not shown). Vacuum isapplied to the chamber 402 under microprocessor control, causing air inthe interior of the test sample cards 28 to evacuate out of theirassociated test tubes and to be withdrawn from the chamber 402. Thevacuum cycle is precisely managed to optimize filling using a closedloop servo system to regulate the rate of change of vacuum and thetiming of the complete vacuum cycle. After a predetermined period, thechamber 402 is vented to atmosphere under microprocessor control. Theventing of the cards causes the fluid in the test tubes 30 to be drawninto the cards 28, filling the wells in the cards 28. After the chamber402 is vented, the chamber is raised up by a vacuum chamber drivemechanism 410 so as to permit the boat to be moved to the other stationsof the machine 20.

The test sample positioning system 100 then operates to advance the boat22 to the right across the rear of the base pan 24 to a cut and sealstation 500, located behind the center mount 34 in FIGS. 1 and 2.Referring to FIGS. 4 and 5, the cut and seal station 500 consists of ahot cutting wire 506 and attached support plate 504, and a drivemechanism 502 (e.g., stepper motor, drive belt and lead screw) thatlowers the cutting wire and support plate 504 to the same elevation asthe top portion of the transfer tubes 32 adjacent to where the transfertubes 32 enter the test cards 28. As the boat 22 is advanced past thecut and seal station 500, the transfer tubes 32 are forced past the hotcutting wire 506. With the assistance of fore and aft constraints placedon the movement of the cards 28 by the walls of the cassette 26, and thelateral constraints on the movement of the card 28 by the cassette andwall structures of the machine 20, the hot cutting wire cuts thetransfer tubes 32 by melting of the transfer tube material as the boat22 is slowly advanced past the hot cutting wire 506. A small stub oftransfer tube material is left on the exterior of the card 28. The stubseals the interior of the card 28 from the atmosphere (except forpossible diffusion of gasses such as oxygen through the tape coveringthe sample wells). When the boat is advanced past the station 500, thewire 506 is raised up to its upper position.

Referring to FIGS. 1 and 3, the test sample positioning system 100 thenadvances the boat 22 across the rear of the base pan 24 behind thecenter mount 34 to a carousel incubation station 600. A reciprocatingrack and pinion driver 610 is mounted to the center mount 34 opposite aslot 602 in the machine that pushes the cards off the cassette 26 one ata time through the slot 602 into a carousel 604. The carousel 604 ishoused in an enclosure that is maintained at an appropriate incubationtemperature for the particular assay, for example, 35 degrees C. Theenclosure is partially broken away in FIGS. 1 and 2 in order to show thecarousel 604. The carousel 604 is rotated by a drive system 612 insynchronism with the movement of the boat 22 over the rear of the basepan 26 by the test sample positioning system 100, so as to place thenext slot in the carousel 604 in line with the slot 602 opposite thenext card in the cassette 26. If the carousel is only going to bepartially loaded with cards, the operating system of the machine maycontrol the carousel 604 rotation to load the cards into non-adjacentslots to equally distribute the cards in the carousel in order tobalance out the weight distribution in the carousel 604. For example,where the carousel has 60 slots and only 30 cards are to be processed,the cards could be loaded into every other slot.

Additional incubation capacity required for processing a larger numberof cards at one time can be provided by adding an additional incubationstation(s) to the rear of the basepan, and adjusting the dimension ofthe base pan and drive system components as necessary. Additional opticsstations may be provided for additional carousels. For example, if thecarousel 604 has sixty slots and each cassette holds 15 cards, fourboats can be processed at once. If a second carousel is added, up to 120cards could be processed at once. Of course, different capacities couldbe provided for the cassette 26 and the carousel 604. Additionalpipetting and diluting capacity and vacuum chambers or other functionscould be provided as well.

After all of the cards 28 have been loaded into the slots of thecarousel 604, the boat 22 is advanced along the right hand edge of thebase pan 24 back to its starting position (shown in FIGS. 1 and 2) or toan exit position for removal of the cassette 26 (containing the testtubes, pipettes 302, if any, and transfer tubes remnants) and receipt ofa new cassette. Alternatively, the boat 22 could be moved to an exitstation located, for example, in the rear or right hand side of the basepan 24.

As the cards 28 are being incubated in the incubation station 600, thecards are periodically, sequentially pushed out of the slots of thecarousel 604 at the top of the carousel 604, one at a time, by areciprocating rack and pinion driver 620 and an associated steppermotor. The cards 28 are moved by an optical scanner card transportstation 700 past a fluorescence and transmittance optics station 800having a transmittance substation 802 and a fluorescence substation 804.The wells of the card 28 are selectively subject to sets oftransmittance and/or fluorescence optical testing according to theanalysis needed to be performed by the transmittance and fluorescenceoptics station 800. The transmittance and fluorescence optics station800 includes detectors and processing circuitry to generatetransmittance and fluorescence data for the wells in the cards 28, andto report the data to a central processing unit for the machine 22. Ifthe test is not complete, the transport station 700 moves the card 28back into its slot in the carousel 604 for more incubation andadditional reading.

Typically, each card will be read every 15 minutes as the carousel makesone revolution. Typical incubation times for the cards 28 are on theorder of two to eighteen hours, consisting of roughly four transmittanceand/or fluorescence data sets per hour for each of the wells in the card28 subject to the optical analysis requirements.

After the testing is complete, the cards are moved by the opticalscanner transport system 700 into a card output station 900 shown inFIG. 2 and FIG. 3. The card output station 900 consists of a detachabletray or magazine 902 and associated support structure that is positionedto the side of the optical station 800 at approximately the sameelevation as the optical station 800. The station 900 has a pressureslide that 914 that is moveable within the magazine 902 and a constantforce spring biasing the pressure slide towards the front of themagazine. The cards are stacked in the magazine between the pressureslide 914 and oppositely opposed resilient snap elements integrallyformed in the sides of the magazine 902. The technician removes themagazine 902 from the machine 20 as needed or when the magazine is fullof cards, empties the cards into a suitable biohazard disposal unit, andreplaces the magazine 902 back into the machine 20.

Test sample positioning system 100

Referring now in particular to FIG. 6, the test sample positioningsystem 100 will be described in detail. The system 100 is shown in aperspective view in FIG. 6 with all of the stations mounted to thecenter mount 34 and the incubation station 600 removed in order to moreclearly illustrate the components of the positioning system 100.

The system 100 has a base pan 24 mounted to a table support structure18, across which the boat 22 is pulled from station to station in themachine 22. The base pan 24 in the preferred embodiment is ofrectangular shape having four sides at right angles to each other: afront side, a left hand side (LHS), a rear side, and a right hand side(RHS). The four sides allow the boat 22 to be moved clockwise in a loopabout the machine back to its starting position at a loading station(shown in FIGS. 1-2) after all of the operations on the sample card 28have been completed. However, the inventive principles of the testsample positioning system are applicable to other geometries for a basepan 24. Additionally, the paddles and motors are capable of moving theboat 22 in a counter-clockwise direction.

The boat 22 has four downwardly depending feet 72 at its four cornerswhich fit in a pattern of track sections comprising grooves 36 formedbetween a set of raised ridges 37 and a raised rim 39 extending aroundthe perimeter of the base pan 24. The grooves 36 help prevent anyrotation of the boat 22 as the boat 22 is pulled over the base pan 24.

When the boat 22 is initially located at the loading station, as shownin FIG. 7, the left front LF and right front RF feet of the boat 22 arepositioned in groove 36A, the right rear (RR) foot 72 is in groove 36D,with the RF foot at the intersection of grooves 36A and 36D. A pluralityof slots 35 are provided in the raised ridges 37 so as to permit thefeet of the boat 22 to move through the ridges 36 as the boat 22 ismoved about the base pan 24. For example, slot 35D permits the rightrear RR foot to move past raised ridge 37D, and slot 35B permits theleft rear LR foot to move past the ridge 37B into the groove 36B. Thecenter mount has a corner 33 that is preferably given a sharp contour,as shown, so as to prevent the boat from undergoing rotation as it isslid along the left hand side of the base pan.

In order to move the boat 22 clockwise about the base pan, fourindependent drive systems are provided for moving the boat 22. Eachdrive system moves the boat 22 in one direction along one of the foursides of the base pan 24. Referring now in particular to FIG. 6, a firstdrive system is provided for moving the boat 22 along the front edge ofthe base pan 24, and consists of a rotatable shaft 42A having a squarecross section, a collar 40A slideably mounted the shaft 42A, a drivebelt 44A mounted to the collar for sliding the collar 40A along theshaft 42A, a stepper drive motor 48A driving a belt 50A, a pulley 52Afor moving the drive belt 44A back and forth along the front edge of thebase pan, and a second pulley 46A for the drive belt 44A. A paddle 38Ais mounted to the collar 40A, and is provided for engaging one or morecomplimentary surfaces on the side of the boat 22. When the drive motor48A is operative to move the belt 44A such that the collar 40A is movedto the left along the shaft 42A, the paddle 38A drags the boat 22 to theleft across the base pan 24.

A shaft rotate motor 54A is also provided with an associated belt andpulley (not shown) for rotation of the shaft 42A by an angle of 90degrees. When the shaft rotate motor 54A rotates the shaft 42A such thatthe head of the paddle 38A is in a horizontal position in the directionof the boat 22, the paddle 38A is in a position to engage acomplimentary surface on the side of the boat 22 so as to drag, the boat22 as the paddle 38A and collar 40A are moved along the shaft 42A. Whenthe boat has reached the end of its travel along the front edge of thebase pan 24, the shaft rotate motor 54 rotates the shaft 42A 90 degreesin a direction such that the paddle 38A is rotated upwards away from theside of the boat 22, thereby disengaging the paddle 38A from the boat22.

Each of the other three drive systems in the sample positioning system100 is functionally equivalent to the drive system described above forthe front edge of the base pan 24, and each is composed of likecomponents. For example, the left hand side LHS drive system has a shaft42B, collar 40B with attached paddle 38B, drive belt motor 48B, shaftrotation motor 54B etc. Like components for the rear edge of the basepan include a rotatable shaft 42C, belt drive motor 48C, etc. Similarly,right hand side (RHS) drive system has a rotatable shaft 42D, collar 40Dand attached paddle 38D, etc.

Dilution station 200

The diluting station of FIG. 1 is shown in more detail in FIGS. 8-10.FIG. 8 is perspective view of the diluting and pipetting stations 200and 300, respectively. FIG. 9 is an elevational view of the stations,and FIG. 10 is a side elevational view of the diluting station 200.

The diluting station 200 can be thought of as a system for dispensing acontrolled volume of fluid into a receptacle such as a test tube. Thestation 200 has a source of diluent fluid 204, such as a flexible bag ofsaline solution, that rests on a suitable inclined shelf 203. A rotatingshot tube 202 having a predetermined volume receives the fluid from thesource 204 via a conduit or tube 206. A filter 208 is placed in theconduit 206, and serves to prevent contaminants from entering the line206.

A solenoid 220 is provided for controlling the opening of a resilientthimble valve placed within the open end 201 of the shot tube 202. Thethimble valve controls the flow of the fluid from the conduit 206 intothe shot tube 202 by obstructing an intake port for the conduit 206 whenthe valve is closed, and opening up the port when it is in an opencondition. Since the source of fluids 204 is placed above the shot tube202, the fluid fills the shot tube 202 by gravity flow. The shot tube202 is mounted to the solenoid 220 housing. The solenoid 220 andattached shot tube is rotatable via a motor 219 (FIG. 10) having a drivebelt and pulley (not shown) relative to a bulkhead 214. The motor 219 isplaced directly behind the solenoid 202 on the back side of the bulkhead214.

When the shot tube 202 is rotated to a generally upward orientation(i.e., the tip of the shot tube is elevated with respect to the end 201of the shot tube), as shown in FIGS. 1, 3 and 4, the shot tube can befilled with fluid such that the shot tube is automatically primed as itis filled. The upward orientation of the shot tube 202 permits airwithin the shot tube to be eliminated from the shot tube 202 as thefluid enters the end 201 of the shot tube and works its way up to thetip of the shot tube 202. An optical sensor 218 mounted to a bracket 216is provided for detecting when the diluent fills the shot tube up to thefill zone adjacent to the tip of the shot tube 202.

When the shot tube 202 is filled, the motor 219 behind the bulkhead 214rotates the solenoid 220 and shot tube 202 in the direction of the arrow222 (FIG. 9) to a second position, wherein the tip portion of the shottube 202 is oriented downwardly towards a test tube in the boat 22 (FIG.1). A second conduit 210 is provided which is in communication with asource of compressed air 217 mounted behind the bulkhead 214. A filter212 is provided in the conduit 210, and prevents contaminants fromentering the line 210. The conduit 210 is fitted over an exhaust tube inthe shot tube 202 in the vicinity of the thimble valve. When the shottube 202 is in the second downward position, compressed air is injectedinto the shot tube in a stream to exhaust the diluent from the shot tube202 into the test tube 30B (FIG. 1).

The solenoid 220 drives a piston along a solenoid axis 221, and a caminside the solenoid couples the piston to a plunger that moves along theaxis of the shot tube 202. The plunger has a tip that is received in theinterior of the thimble valve. When the plunger is activated to anextended position by the solenoid 220, the tip of the plunger pushesagainst the central wall of the thimble valve and distorts the shape ofthe thimble valve, allowing fluids to flow around the edge of thethimble valve into the interior of the shot tube 202. When the solenoid200 retracts the piston, the thimble valve assumes its normal positonflush against the interior of the shot tube sealing off the fill tubeport.

Pipetting station 300

The pipetting station 300 is shown in FIGS. 8 and 9 in an overallaspect. The station 300 includes a pipette hopper 304 and dispensingassembly shown in an end view in FIG. 12 and an exploded view in FIG.13.

Referring to FIGS. 8, 9, and 11-13 in particular, the station 300includes a generally cylindrical housing or hopper 304 that contains aplurality of hollow pipette straws 320. As seen in FIG. 12, the housing304 has a horizontally disposed straw withdrawal opening slot 350 at thebottom of the housing 304. The housing 304 is mounted to a block 306which is rotatable relative to a bulkhead 310 by a pin 308 secured tothe bulkhead 310, so as to permit the housing 304 to rotate upwards fromthe orientation shown in FIG. 1 to the orientation shown in FIG. 11. Thehousing includes a clear plastic cover 305 which prevents the straws 320from falling out of the housing 304. The plastic cover 305 is mounted tothe housing 304 via a screw 303 and a mounting hole 307 (FIG. 13) in thehousing 304. As shown in FIG. 11, the plastic cover 305 swings out froma position covering the housing 304 opening so as to permit a technicianto refill the housing 304 with straws 320.

When the housing 304 is in the normal, horizontal position in FIGS. 1and 12, the slot 350 is positioned immediately above a horizontal slidemember 314. Referring to FIG. 12, the horizontal slide 314 has asolenoid 336 that is mounted to the back side of the bulkhead 310 formoving the slide between extended and retracted positions. The solenoid336 could be mounted to the front of the bulkhead in a differentconfiguration if desired. The movement of the slide 314 is accomplishedby moving a shaft 338 that the slide 314 is mounted to back and forth.The slide 314 is slid along guides 337.

A stepping motor 312 (FIGS. 9 and 13) mounted to the rear wall of thedrum 340 is provided to sweep a rotatable drum 340 having threeequidistantly spaced fingers 342 about the interior surface of thehousing 304. In a preferred embodiment, each of the fingers 340 define asweep angle α of approximately 60 degrees. As best seen in FIG. 12, asthe fingers 342 sweep along the interior surface of the housing 304, oneof the fingers sweeps a straw 320 in the housing 304 into the slot 350.The fingers 342 stop their movement such that a portion of the finger342 covers the slot 350, with a straw positioned below the finger in theslot, as shown in FIG. 12. When the horizontal slide 314 is in theposition 314' shown in dashed lines in FIG. 12, the top surface 354 ofthe end portion 356 of the slide 314 is positioned below the slot 350 incontact with a bottom housing surface 352, preventing a straw 320 fromfalling out of the housing 304 through the slot 350. As shown best inFIG. 12, the sides of the slot 350, the finger 342 and the slide 314 allcooperate to firmly retain the straw 320 in the slot, permitting thetapered tubular transfer pin 330 to be inserted into the end of thestraw 320.

Referring to FIG. 12, the housing 304 is made from a low frictionmaterial. Preferably, the housing 304 is constructed such that theinside diameter of the housing 304 is less than the length of thehousing, so as to maintain the straws 320 in a condition orientedparallel to the length of the housing 304, so that they can be readilyswept into the slot 350.

While the slide 314 is in the extended position 314' and the straw istrapped in the slot 350 as shown in FIG. 12, a tapered tubular transferpin 330 (FIGS. 9, 13) is moved from a retracted position in a transferpin assembly 316 into an extended position directly into the straw 320in the slot 350, so as to frictionally engage the tip of the straw 320.At this point, the horizontal slide 314 retracts towards the bulkhead310. The transfer pin 330 now is rotated by a motor 360 (FIGS. 14-16) toa vertical position as shown in FIG. 1, permitting the straw 320 to bemoved through the slot 350 out of the housing 304. As soon as the straw320 is rotated out of the slot 350, the slide 314 is moved back to theposition 314' shown in dashed lines in FIG. 12, and the motor 312 isoperated to sweep another straw 320 into the slot 350.

The tapered tubular transfer pin 330 with attached straw 302, now in avertical orientation directly above one of the test tubes in thecassette 26, is lowered so that the end of the straw 302 (FIG. 1) isimmersed sufficiently into the fluid in one of the test tubes (e.g. testtube 30A), such as a test tube containing a biological or control fluidsample. Vacuum is applied to the tubular transfer pin 330 and attachedstraw 302 for a predetermined period of time, drawing a precise andcontrolled volume of fluid into the straw 302. The tubular transfer pin330 and attached straw (with fluid) is raised up so as to clear the topof the test tube. The boat and test tube are advanced by the positioningsystem 100 by an amount equal to the separation distance of adjacenttest tubes. The tubular transfer pin 330 and straw 302 are lowered intothe susceptibility test tube 30B, whereupon the vacuum applied to thetransfer pin 330 is released, causing the fluid contents of the straw302 to fall into the susceptibility test tube 30B. At this point, thetubular transfer pin 330 is moved to a position wholly within thetubular transfer pin housing so as to eject the straw 302, dropping thestraw in the susceptibility test tube. The transfer pin assembly 316 isthen raised back to the elevation of the hopper 304, rotated into ahorizontal position, and the process repeated.

Referring to FIGS. 14, 15 and 16, the transfer pin assembly 316 andassociated motor and vacuum system for the transfer pin 330 areillustrated in greater detail. Referring to FIG. 14 in particular, amotor 322 is mounted behind the bulkhead and includes a drive belt 324that turns a pulley 326 and a threaded shaft 362, referred to in the artas an ACME thread or lead screw. A transfer pin plate 361 is mounted tothe threaded shaft via a pair of collars 364. Depending on the directionthat the motor 322 rotates the shaft 362, the plate 361 and attachedtransfer pin assembly 316 is slid either up or down the two pillars 359between an upper position, in which the transfer pin 330 is at the sameelevation as the straw withdrawal slot 350 in the housing 304, and alower position in which the straw 302 is in a position to withdraw fluidfrom a receptacle placed below the transfer pin assembly 316.

A second motor 360 having a drive belt 363 and pulley 365 is mounted tothe rear of the transfer pin plate 361, and is provided for rotation ofthe entire transfer pin assembly 316 in the direction of the arrow ofFIG. 14 between a first position, in which the transfer pin 330 isoriented in the direction of the straw withdrawal slot 350, to a secondposition, in which the straw 302 is oriented vertically downward in theposition shown in FIGS. 1 and 14.

Referring to FIG. 15, the transfer pin assembly 316 is illustrated in aside view as seen from the pipette housing 304. The transfer pinassembly has a transfer pin housing 331 which defines a transfer pinaperture 368. The tapered tubular transfer pin 330 (FIG. 16)reciprocates between a retracted position in the housing (shown in FIGS.15 and 16), and an extended position shown in FIG. 14 at which itengages a straw in the straw withdrawal slot 350 as shown in FIG. 13. Atransfer pin actuation solenoid 370 is mounted to the rear of thetransfer pin assembly 316 to move the tubular tapered transfer pin 330between the retracted and extended positions. A source of vacuum 366 ismounted adjacent to the transfer pin housing 331, and provides vacuum tothe end of the transfer pin 330 via a tube 372. A vacuum pressuretransducer P is provided which monitors the vacuum generated by thesource 366 to ensure that a straw is attached to the tapered tubulartransfer pin 330, that fluid is withdrawn into the straw, and that asufficient volume of liquid is transferred. This pressure transducer Pis positioned at the end of a secondary vacuum line 373 in communicationwith the vacuum source. A suitable pressure transducer P is the Motorolamodel MPX 5010D sensor.

When the transfer pin 330 and straw 302 are rotated from a horizontalposition to the vertical position shown in FIG. 14, the straw 302 isrotated out of the slot 350 in the housing 304. The motor 322 thenoperates to lower the transfer pin assembly 316 to the appropriate levelsuch that the straw 302 is immersed in the test tube 30A. Afterwithdrawal of the fluid from the test tube 30A, the motor 322 raises thetransfer pin assembly 316 up such that straw 302 clears the top of thetest tube 30A, and then lowers the assembly 316 into test tube 30B aftertest tube 30B is placed below the straw 302. To remove the straw 302,the transfer tube 330 is retracted into the transfer tube housing 331.The diameter of the straw 302 is slightly larger than the diameter ofthe transfer pin aperture 368, forcing the straw 302 off of the transferpin 330 as the transfer pin 330 with completely withdrawn into thetransfer pin housing 331 in the position shown in FIG. 16. In thisembodiment, the straw 302 falls into test tube 30B. The transfer pinassembly is then rotated back into a horizontal position and raised tothe level of the straw withdrawal slot 350 in the housing 304, and theprocess is repeated for the next set of test tubes.

Vacuum Control of Card Loading

At the vacuum station 400, the vacuum loading of the cards 28 in thevacuum chamber 402 is controlled in a manner to prevent the formation ofbubbles in the wells of the cards 28. The station 400 is shownschematically in FIG. 29.

The vacuum filing station 400 consists of the following components:

A vacuum pump 420 (Gast P/N: SAA-V110-NB, 115 VAC, 50/60 Hz, 29.5 inchHg max. Vacuum: 1.75 cfm open flow).

A proportional vacuum control valve 422 (Honeywell/Skinner P/N:BP2EV0006, 12-24 VDC, 0-5 VDC Control. 0.078 inch diameter orifice).

A 4-way direct acting solenoid valve 424 (Humphrey P/N: 420 24 VDC, 60scfm @ 1100 PSIG inlet pressure, 24 VDC, 0.250 inch diameter orifice).

An air filter 426 (Norgren P/N: F39-222EOTA, 4 scfm @ 100 PSIG inletpressure, 0.01 micron filtration).

An absolute pressure transducer 428 (Dara Instruments P/N: XCA415AN,Range: 0-15 PSIA, 5 VDC Excitation, 0.25-4.25 V F.S.O., +/-0.5% ofF.S.O. Combined Linearity & Hysteresis, +/-0.3% of F.S.O.Repeatability).

A standard sample preparation node (SPN) printed circuit board 430.

Vacuum tubing 432, 0.250 inch inside diameter.

The drive system 410 for the station 400 includes a stepping motor 438and associated belts 440 and threaded shafts 442 that raise and lowerthe vacuum chamber 402. An optical encoder 434 and optical interrupt 436sense when the vacuum chamber 402 is at its upper and lower positions,respectively.

When the vacuum pump 420 is turned on, it pulls free air through thefilter/muffler 444 attached to the 4-way solenoid valve 424. To fill thecard 28 in the boat 22, the following sequence occurs: The vacuumchamber 402 is lowered onto the boat 22 with the sample cards 28. Theproportional and vacuum control valve 422 is opened 100%. The 4-waysolenoid valve 424 is energized and air is pumped out of the vacuumchamber 402 through the air filter 426 and the 4-way solenoid valve 424.The absolute pressure transducer 428 gauges the vacuum chamber 402pressure decrease and sends a proportional continuously changing voltageoutput to the SPN Board 430. The continuously changing voltage issampled by the SPN Board 430 at regular intervals and the rate of changeis compared to the programmed rate to pump down the vacuum chamber.

If the rate of change is too fast, the proportional valve 422 is sent ahigher control voltage to open wider, if possible, and increase the sizeof the air leak into the vacuum line 406. If the rate of changes is tooslow, the proportional valve 422 is sent a lower control voltage toclose down, if possible, and decrease the size of the air leak into thevacuum line 406. The control of the rate of change of pressure insuresthat vacuum is not drawn too quickly, which can cause splashing andbubbles in the test tubes 30. This can cause air bubbles to enter thecard 28 when the chamber is vented, interfering with the opticalanalysis of the card.

The absolute pressure transducer 428 continues to gauge the vacuumchamber 402 pressure and send the proportional pressure voltage to theSPN Board 430 while the 4-way solenoid valve 424 is deenergized. Thevacuum pump 420 is turned off, and the proportional valve 422 is closedcompletely for five seconds when the vacuum target (or set point)pressure of 0.90 PSIA is reached. This is to prevent the possibility ofthe pressure in the vacuum chamber from varying up and down enough toallow sample fluid to be transported in and out of the test card 28during the five second dwell period.

The absolute pressure transducer 428 continues to gauge the vacuumchamber 402 pressure and send the proportional pressure voltage to theSPN board 430, while the proportional valve 422 is opened gradually atthe end of the five second vacuum dwell period until the programmedpressure increase rate of change is achieved.

The continuously changing voltage from the pressure transducer 428 issampled by the SPN Board 430 at regular intervals and the rate of changeto return to atmospheric pressure is compared to the predeterminedprogrammed rate. If the rate of change is too fast, the proportionalvalve 422 is sent a lower control voltage to close down, if possible,and decrease the size of the air leak into the vacuum line 406. If therate of change is too slow, the proportional valve 422 is sent a highercontrol voltage to open wider, if possible, and increase the size of theair leak into the vacuum line 406. This steady controlled ventingpermits fluid samples to be drawn into the sample cards 28 in a mannerto reduce the risk of bubbles forming in the wells of the card 28, andto insure complete filling of the card 28.

The proportional valve 422 is opened 100% at the complete return toatmospheric pressure and held open while the vacuum chamber 402 israised from the boat 22. This is to prevent a residual vacuum fromoccurring in the chamber 402 and lifting the boat 22 within the chamber402. The proportion valve is closed and the system is ready to repeatthe cycle.

The vacuum generation, dwell, and venting cycle is illustrated ingraphical form in FIG. 30. Note the linear draw down curve 450 of about-0.54±0.07 PSIA per second, the 5 second dwell period 452 at 0.90 PSIA,and the linear vent rate curbe 454 of about +0.45±0.07 PSIA per second.

For the illustrated embodiment, it is assumed the relative pressurebetween the test card 28 and the surrounding atmospheric media insidethe vacuum chamber 402 to be 0 PSI. In reality, there should be a verysmall pressure difference inside the test card 28 versus outside thetest card 28 in the vacuum chamber throughout the filling cycle. If,however, one considers the pressure changes inside versus outside thevacuum chamber, then the following cycle information applies to theillustrated embodiment: Initial: local atmospheric pressure (varies withlocal barometric pressure). Start filling cycle: -0.53+/-0.07 PSI/sec(23-30 seconds pump down). Vacuum dwell: Approx. 5 seconds. Return toatmospheric pressure: +0.53+/-0.07 PSI/sec (23-30 seconds return). Areturn to atmospheric rates faster than this can causes some test cardfills to be incomplete. End: Local Atmospheric Pressure (same asinitial).

Transfer Tube Cut and Seal Station 500

Once the card is filled with sample in the vacuum chamber 402, thecassette 26 is moved through a transfer tube cutting and sealing station500, best seen in FIGS. 1, 4, and 5. A formed nichrome wire 506 isheated to a precise temperature for cutting through the transfer tubes30 using a microprocessor-controlled constant current source (notshown).

The cassette 26 is moved past the hot wire 506 at a slow speed to allowthe wire to cut and seal the transfer tubes 30 close to the card 28,forming an external transfer stub. The remainder of the transfer tube 30remnant is left in the test tube for disposal, as shown in the extremeright hand side of the boat 22 in FIG. 5.

The hot cutting wire 506 is mounted to a mechanism including plates 504that are raised and lowered by a stepper motor/pulley/drive belt driveassembly 502 (FIG. 1), allowing the wire 506 to be moved out of the wayto allow un-cut transfer tubes to be moved past the cutting and sealingstation 500. This function can be used to batch load multiple cassettesor for error recovery purposes.

The cutting and sealing station 500, in cooperation with the test samplepositioning system 100, enables multiple transfer tubes to be cutessentially at once as the boat 22 is advanced past the hot cutting wire506. Control of the cutting of the transfer tube to produce a reliableseal is accomplished by using a constant current source to control theheat output of the hot cutting wire 506, and controlling the speed atwhich the boat 22 and cassette 26 is moved past the wire 506. Since theelectrical properties of the wire 506 are predetermined, and by holdingthe current constant and controlling the speed at which the wire passesthrough the plastic transfer tube 30 (i.e., the speed of motor 48C), thestation 500 can simply and precisely control the cutting and sealing ofthe transfer tube 30. This heat control design is very simple and doesnot need temperature calibration. The wire 506 heats up very quickly, sothe wire does not have to be left on all the time. This feature offerssafety and energy conservation advantages.

In the prior art cutting and sealing station of the Vitek® sealer, ablock of metal is with a cartridge heater embedded with a thermocoupleconnected to a conventional temperature control. This is a fairlyexpensive, bulky device that needs calibration, cuts only one straw at atime, and requires a long, constantly "ON" heating time. In contrast,the present inventive sealing station 500 is much smaller, morereliable, and less expensive to manufacture. Rather than controllingtemperature, as in the prior art, the station 500 controls the powerwith a constant current source applied to the cutting/sealing wire 506to control heat. Heat is a function of the square of the current sincepower (P)=I² R. Typically, the setting for the constant current sourceis set at the factory once and would not have to be adjusted in thefield.

Optical Scanner Transport Station 700

Referring now to FIG. 17, the sample card transport station 700 for theoptical scanners is shown in an elevational view. The station 700includes a drive assembly 702 having a cover plate 704 which is mountedto a bulkhead or support 706. The optical reader system 800 in thepreferred embodiment consists of a transmittance substation 802 and afluorescence substation 804 mounted to the bulkhead 706, the outlines ofwhich are shown in FIG. 17. The sample card 28 is moved from the top ofthe carousel 604 by the drive assembly 702 through the optical readersystem 800 and back to the carousel 604 if the card 28 needs furtherincubation and additional reading. If the card has been sufficientlyincubated (based on the analysis of data from the optical reader system800), the card 28 is moved to a card reject tray 902 (FIGS. 2 and 3) tothe left of the optical system 800.

The drive assembly 702 consists of a stepper motor 708, shown in dashedlines, positioned behind a mounting bracket 709. The motor 708 drives atiming pulley 711 that moves an endless, substantially inelastic, drivebelt 710 having teeth 710 over a series of rollers 712. The belt 710 issupported at the top of the cover plate 704 by a set of rollers 712. Thepath of the belt through the rollers 712 is shown in dashed lines inFIG. 17. It can be seen that the belt 710 passes across the top of thecover plate 704 and beneath the optics in the optical substations 802and 804. The drive belt 710 engages the bottom edge of the card 28 alongthe top of the cover plate 704. A suitable drive belt 710 can beobtained from the Gates Rubber Co., of Denver, Colo.

A ledge 718 mounted to the bulkhead 706 is provided above the belt 710and the optical reading system 800. The ledge has a slot 720 whichreceives the upper edge of the card 28. The ledge 718 and slot 720defines a card travel direction. When the card 28 is pushed out of thecarousel 604, the card 28 is snugly positioned in the space between theslot 720 and the belt 710. The entire drive assembly 702, includingcover plate 704, stepper motor 708 and drive belt 710, is movablerelative to the support bulkhead 706. To permit the relative movement, aset of carriage and slide assemblies 716 are provided, one of which isshown in more detail in FIG. 19. As seen in FIG. 19, each of thecarriage and slide assembly 716 includes a slide 730 mounted to thebulkhead 706 by a bolt 734. The carriage 726 is mounted to the coverplate 704 by a set of four screws 724. The carriage 726 slides relativeto the slide member 730 by means of ball bearings 728 which slide alonga groove 732. In the preferred embodiment, two of the carriage and slideassemblies 716 are provided, one on each side of the cover plate 704.

The entire drive assembly 702 is biased upwards towards the ledge 718 bybiasing springs 714. The springs have a top end 713 engaging a pinmounted to the bulkhead 706, and a bottom end 715 engaging a pin mountedto the cover plate 704. Three springs 714 in all are preferred, and areplaced at the center and sides of the cover plate 704. The springs 714each have a spring constant K of 16.5 lbs/in., for a total of 49.5lbs/in for the three springs. The purpose of the springs 714 is toconstantly maintain the proper upward pressure on the card 28 by thebelt 710, such as in the case of some tolerance variation in the heightof the cards. The drive belt 710 must provide enough upward force so asto permit the belt to engage the bottom of the card 28 and move the cardalong the slot 720, but not too much to cause binding by the drive motoror too little force, which would cause the belt to slip relative to thebottom of the card. By maintaining the proper upward force on the card,such that belt travel is directly translated into card travel, precisemovement by the stepper motor 708 results is precise movement of thecard 28 relative to the optical system 800. This precise movement isdiscussed in greater detail in conjunction with the operation of thetransmittance substation 802.

Referring to FIG. 18, the drive assembly 702 and bulkhead 706 are shownin a side view, looking towards the carousel 604 and incubation station600 of FIG. 17. The rollers 712 at the top of the cover plate 704 form aslot, as shown, which helps support the bottom edge of the card 28. Thecard 28 is snugly positioned between the belt 710 and the slot 720 inthe ledge 718. The upward force on the card 28 by the springs 714 causesthe belt 710 to grip the bottom edge of the card 28, such that the card28 is slid along the ledge 718 by the drive belt 710 without anysignificant slippage between the belt 710 and the card 28. To facilitatethe sliding motion, the slot 720 is made from a low friction materialsuch as Delrin or given a low friction coating. The bottom edge of thecard 28 can be provided with a knurled texture surface such as parallelraised ridges to better enable the belt 710 to grip the card 28 as thebelt 710 moves backward and forwards over the rollers 712.

When the leading edge of the card 28 reaches the transmittancesubstation 802, an optical interrupt LED in the transmittance substationtransmits radiation through an optical interrupt aperture 112 at thebase of the card 28. An optical interrupt detector senses the radiationand sends a signal to the control system to cause the motor 708 to stop.When the motor 708 stops, the first column of wells 110 in the card 28are positioned directly opposite a set of eight transmittance LEDs inthe transmittance substation 802, which conduct transmittance testing ofthe column of wells in the card 28.

After an initial illumination of the LEDs, the motor 708 is operated torapidly move the belt 710 in a series of small steps, such that thetransmittance optics luminates the individual wells at a series ofpositions across the width of the wells. This precise movement of thecards 28 achieves a large set of data for the wells 110. Thetransmittance testing at multiple positions across the wells 110 willlikely include a detection of any air pockets or debris in the wells,enabling the data processing system to detect and possibly reject anabnormal transmittance measurement.

Where fluorescence testing is called for, after all of the wells of thecard 28 have been subject to the transmittance testing by transmittancesubstation 802, the motor 708 and belt 710 slides the card 28 to thefluorescence substation 804, wherein fluorescence testing of the wells110 takes place.

Depending on the test status, the card 28 is then either returned to thecarousel 604 by moving the motor 708 and belt 710 in the reversedirection, or else the motor 708 and belt 710 are operated to move thecard all the way to the left hand edge of the drive assembly 702 toplace the card 28 in the card disposal mechanism 900.

Fluorescence Optics Substation 804

Referring now to FIG. 20, the fluorescence optics substation 804 isshown in a perspective view isolated from the machine 20. The substation804 includes a reflector assembly 806 mounted via a hinge 808 to anoptical head 810. The optical head 810 has a plurality of surfaceapertures 812 defining six optical channels between a fluorescenceillumination source and the middle six wells in a column of wells in thecard 28. The illumination source is placed within a flashlamp cassette816.

When the hinge 808 is in a closed condition, the reflector assembly 806is positioned parallel to the apertures 812. The card 28 is moved backand forth in the space defined by the front surface apertures 812 andthe reflector assembly 806. An LED and detector cooperate with theoptical interrupt aperture 112 along the base of the card 28 toprecisely position the card in the space between the front surfaceaperatures and the reflector assembly.

The reflector assembly 806 has a stepper motor 801 which moves anoptical shuttle 803 back and forth along guides 807. A reflector 852 anda solid reference 850 are mounted to the optical shuttle 803. Thepurpose of the reflector and solid reference are described in moredetail below. In normal operation, the shuttle 803 is in a position suchthat the reflector 852 is placed directly opposite the apertures 812 ofthe optical head 810. Whenever a calibration of the detectors in theoptical head 810 is performed, the motor 801 moves the shuttle 803 suchthat the solid reference 850 is placed in the optical path opposite theapertures 812. The reflector assembly housing includes a housing for anLED for the optical interrupt aperture 112 for the card 28. A springclamp 805 is provided to secure the reflective assembly to the head 810when the assembly 806 is in a closed condition.

Referring again to FIG. 20, the flash lamp cassette 816 holds anelongate xenon linear flash lamp, which serves as a fluorescenceillumination source for the fluorophores placed in the wells 110 of thecard 28. The flash lamp cassette 816 is connected to a high voltagepower supply 820. A peak detector 814 and electronics module is mountedbehind the optical head 810. The flash lamp cassette 816 includes ainterface block 854 and a lamp holder 856.

Referring now to FIG. 21, the fluorescence optics substation 804 isshown in a sectional view perpendicular to the axis of the flash lamp824 and the six photodiode detectors. The flash lamp cassette 816 housesthe single elongate linear xenon lamp 824, which is mounted at the focusof an elongate cylindrical parabolic reflecting mirror 822. Theflashlamp 824 has a high current capacity connection allowing fieldreplacement of the lamp. This is unique for this lamp type due to thehigh pulse currents generated during the flash (over 350 amps).

The flash lamp radiation R is reflected off of a cold mirror 826 onto a365 nM filter 828, which filters the radiation R to pass radiation atthe excitation wavelength of the fluorophores. After passing through thefilter 828, the radiation R reflects off a dichromatic beam splitter 830along its optical path 833 and out of the apertures 812 and into thecard wells 110. Any radiation passing through the wells 110 is reflectedoff the reflector 852 in the reflector assembly 806 and reflected backinto the wells 110. The radiation excites the fluorophores in the well110, causing the fluorophore to briefly to emit radiation. The emissionradiation is shown as a dashed line in FIG. 21. The emission radiationpasses through the dichromatic beam splitter 830, through a focusinglens 836 and band pass filter 838 onto a photodiode detector 840. Thereare six photodiode detectors in all for the six optical channels.

The use of a selective reflector 852 enhances the signal-to-noise ratioand minimizes optical cross-talk by doubling the optical path. Further,when the card 28 is positioned for reading by the fluorescence stationby means of the optical interrupt, the wells in the card are oriented tominimize cross-talk and maximize the fluorescence signal. The card 28material is preferrably opaque to minimize cross-talk, and white tomaximize the fluorescence signal.

The dichromatic beam splitter 830 is highly reflective to radiation atthe excitation wavelength of the fluorophores, reflecting approximately95% of the radiation into the well 110. However, the dichromatic beamsplitter 830 is highly transmissive to radiation at the emissionwavelength of the fluorophores, passing most of the radiation from thefluorophore along the same optical path 833 onto the detectors 840.

Approximately 5% of the radiation from the lamp 824 that is notreflected off the dichromatic beam splitter 830 is transmitted along anoptical path 834 to a mirror 832. The mirror 832 reflects the radiationthrough a focusing lens 836A and a band pass filter 846 to a referencephotodiode detector 844. The reference detector 844 is used by the peakdetector circuit 814 to compute the ratio of the signal detected by thedetectors 840 divided by the signal detected by reference detector 844.The output of the lamp 824 may vary over time, however the ratio of theoutput of the channel 840 detector divided by the output of thereference detector 844 remains constant, i.e., independent of changes inlamp output over time.

In addition to compensating for changes in lamp intensity, the referencechannel 844 can also be used to determine if the lamp 824 is providingsufficient light for proper operation of the fluorescence opticalsystem. By monitoring the lamp output at the reference detector 844, thesystem can automatically determine when the lamp 824 needs to bechanged.

Still referring to FIG. 21, the reflector assembly 806 also includes asolid reference 850 which emits radiation at the fluorophore emissionwavelength when the reference 850 is moved into the optical path 833.Preferably, the solid reference 850 is a phosphorescent Europium sourcesandwiched between glass plates and having a 450 nM filter placed overthe front surface of the glass.

The peak detector 814 inputs signals from the six photodiode detectorsto a set of six fixed gain amplifiers that convert the current from thephotodiode to a voltage signal. The lamp reference channel input signalis supplied to a detector and amplifier. The output of the detectors andfixed gain amplifiers are input into a set of variable gain amplifiers.Similarly, the output of the detector amplifier is input to a variablegain amplifier. The variable gain amplifiers supply an output signal toa set of electronic peak detectors.

The electronic peak detectors are all basically the same as the peakdetector described in the standard textbooks, but modified slightly inthat a transconductance amplifier is used as the first stage amplifier,instead of a standard operational amplifier. This allows the circuit tooperate very fast with a minimum of signal distortion over severaldecades of voltage.

The output of the peak detectors is buffered by a buffer amplifier andsupplier to a multichannel input Analog to Digital (A-D) converter. Theoutput of the peak detector from the reference channel is similarlybuffered and supplied to a reference input in the A-D converter. A databus is provided which sends the output of the A-D converter to amicroprocessor-based controller board (not shown) which conducts theprocessing of the signals from the six channels and the referencephotodetector. In particular, the controller board takes the ratio ofthe output of the six channels divided by the output of the referencechannel, to thereby compute a relative fluorescence number which isindependent of the output of the lamp 824.

Once the card 28 is positioned in the fluorescence substation, the lamp824 is flashed at a 25 Hz rate a number of times, such as ten times.After each flash, the A-D converter computes the ratio of each channelto the reference and the controller board reads the results. After 10flashes, the results are signal processed for each channel. This processin conducted in parallel for each of the six channels.

The data bus also supplies control signals to the peak detectors and thevariable gain amplifiers. In the calibration of the detectors, thecontroller board adjusts the variable gain amplifiers so as to provide auniform amplitude across the six channels.

Transmittance Substation 802

Referring now to FIG. 22, a preferred transmittance substation 802 isshown in an elevational view. The substation 802 has up to threetransmittance optical sources 770A, 770B and 770C, each of whichcomprise eight LED sources (one for each well in a column of wells) andan optical interrupt LED source. The optical sources 770A-C areseparated from each other by a separation distance D equal to theseparation distance between the columns of wells 110 in the card 28.Three sources 770A-C are provided so as to enable transmittance testingat three different sets of wavelengths. The source 770A is shown inperspective view in FIG. 23, and has eight LEDS 797 which are separatedfrom each other by a distance L equal to the distance between adjacentwells 110 in the column direction of the card 28. The optical interruptLED 789 shines light throughout the optical interrupt 112 along the baseof the card 28. A set of three columns of transmittance detectors areplaced behind the three sources 770A-C to collect radiation from theLEDs 797 and 789 and supply transmission data to the controller board ina well-known manner.

Referring now to FIG. 24, the transmittance source 770A and itsassociated detector 791 are shown in a sectional view, taken along thelines 24--24 in FIG. 22. The LED source 797 is mounted to a substrate798 in a well known manner and transmits light through the aperture 793to the sample well 110. The radiation falls on the photodiode detector791, which is also mounted to a substrate 792 in a well known manner.The detector 791 is mounted in a housing 795 that extends verticallydirectly opposite the detector 770A. The construction of light source770A and detector 795 is the same for the other two sources anddetectors in the transmittance station 802.

To perform transmittance analysis of the entire well 110, the card 28 ismoved rapidly in a series of small increments relative to the source770A, for example in 10 or 14 positions, and multiple illuminations ofthe well 110 are taken at each position. A presently preferredtransmittance illumination test is fourteen equidistant positions acrossthe entire width of the well 110, and 10 illumination events at each ofthe fourteen positions. This test can be performed at up to threedifferent transmittance wavelengths for every well, resulting in a largeset of transmittance data.

Referring to FIG. 23, as the card 28 is moved out of the carousel 604,the first column 110' in the card is moved to the source 770C havingLEDs of a first wavelength, whereby the 14 movement steps and 10illumination events per step are performed. The card 28 is then advancedsuch that column 110' is positioned opposite the source 770B having LEDsof a second wavelength. The source 770B illuminates the first column110' while the source 770C illuminates the second column. The card 28 isthen moved such that the column 110' is positioned opposite the source770A having LEDs of a third wavelength, and now sources 770A-C alloperate in concert to illuminate three columns of the wellssimultaneously. The card 28 is advanced to the left such that allcolumns are subject to transmittance illumination at the three sets ofwavelengths. A column of LEDS could contain up to eight differentwavelengths in one column if desired. When the last column has beenilluminated by source 770A, the card 28 is moved to the fluorescencesubstation 804 for fluorescence testing.

Of course, the operation of the transport system 700 and transmittancesubstation 802 could be controlled such that the card 28 is movedthroughout the station 802 from left to right instead of right to left.Further, a lesser or even greater number of transmittance sources 770could be used if desired.

Cassette Identification and Bar Code Reading Systems

A. Cassette Identification System

Referring to FIG. 26, in a preferred embodiment a stand-alone cassetteidentification station 80 is provided to facilitate the processing ofthe cards 28 by the machine 20. The station 80 consists of a computerterminal having a monitor 84 and attached keyboard 86 and bar codereader 88. A conventional host CPU and memory are contained in thestation 80, which are not shown. The host CPU runs a menu-drivensoftware program that prompts a technician to enter patient or sampleinformation that is to be associated with each of the cards 28. Thestation 90 has a data port allowing it to communicate with the machine20 or another computer.

The station 80 receives patient and sample data from the technician viaa bar code scanner and/or keyboard 86, stores the information in itsmemory, and associates that information with the bar code 89 that isapplied to the top of the test sample cards 28. The station 80 can havea bar code reader 88 that reads the bar codes 89 applied to the cards28. After the cards have been read, the user is prompted to scan orenter the patient or other information that is associated with the cards28. Bar code cards 83 may be provided with the most commonly entereddata to minimize the typing in of information. After each card 28 hasbeen read and the information associated with it loaded into thecomputer at the station 80, the technician loads the card 28 into acassette 26.

The base portion of the station 80 below the screen 84 is given a moldedcontour so as to snugly receive the cassette 26 and position thecassette 26 as shown, such that the two touch buttons mounted on therear of the cassette 26 are placed into touching contact with the touchbutton data writing terminals 82 for the station 80. After all the cards28 have been loaded into the cassette, the information associated withall the cards is loaded onto the touch buttons via the terminals 82. Thecassette 26 is now ready to be loaded into a boat 22 in the machine 20.

Referring to FIG. 27, the touch buttons are read at an informationretrieval station in the machine comprising touch button readerterminals 85 attached to the side of the center mount 34. As the boat 22is moved along the base pan 24, the touch buttons come into contact withthe reader terminals 85. The data from the touch buttons is passed vialeads 87 to a central processing unit for the machine 20, whichassociates the data with the optical data from the optics station 800.

B. Bar Code Reading Station

Referring to FIGS. 3 and 28, the machine 20 further includes a bar coderea ding station 90 to read the bar codes 89 applied to the cards 28.The bar codes are read by a bar code reader 90 mounted to a bar codereader support structure 92 affixed to the center mount 34. The barcodes are applied to the cards 28 in a location such that when the cards28 are loaded in the cassette 26, the bar codes are along the "top" ofthe card 28, where they can be more easily read.

As the boat 22 and cassette 26 are advanced to the left along the frontof the machine 22, they pass underneath a card separation device 94consisting of wheel 94 mounted to a support piece 96. The support piece96 is mounted via a pin 98 to a bulkhead attached to the center mount34. The support piece 96 is allowed to pivot about the pin 98 as shownby the arrow in FIG. 28, permitting the wheel 94 to ride up and over thecards as the cards 28 pass underneath the wheel 94. In the process ofriding up and over the cards 28, the wheel 94 rocks or pushes the cardsinto a slanted position as shown in FIG. 28, where they can be moreeasily read by a bar code reader 90. Referring to FIG. 28 in particular,as card 28C passes under the wheel 94, the wheel pushes the card 28C inits slot to the slanted orientation shown. The wheel 94 rides up andover the top of the card and performs the same operation on the nextcard 28D, pushing card 28D in to the position 28E shown in dashed lines.The wall 70 height and distance between adjacent walls 70 in thecassette 26 is chosen so as to permit enough rocking motion for thecards 28, but not so much so as to create too much play in thepositioning of the cards 28 in the cassette 26.

The bar code reader 90 station is positioned along the front side of themachine between the loading station and the diluting station 200. Inthis position, the reading station is able to check the validity of thetest prior to filling the card with the sample. This allows the testsample to be saved in the event of an operator or instrument error.

User Interface

While the foregoing discussion and illustrations for the machine 20 havedescribed in detail of the construction and operation of the machine 20,it will be understood that the machine per se has a user friendly andattactive panel covering for aestetic and safety purposes. A userinterface connected to the machine's host CPU is preferrably included onthe front panel, and includes a LCD (liquid crystal display) screen andtouch pad for presenting instrument status information to the operator.It is also used for things such as start tests, request information, andperform diagnostics.

A preferred test sample card 28 for the machine 20 is described inapplication Ser. No. 08/455,534, filed May 31, 1995, which isincorporated by reference herein.

A presently preferred embodiment of the invention has been described.Persons of skill in the art will appreciated the variations andmodifications can be made to the particular details without departurefrom the true spirit and scope of the invention. This true spirit andscope of the invention is defined by the appended claims, to beinterpreted in light of the foregoing.

We claim:
 1. A machine for testing a sample delivered to areagent-filled test card, comprising:at least one loading station forloading said test card into said machine having a tray for receiving atleast one test sample and at least one test card, wherein said at leastone test sample is placed in fluid communication with said at least onetest card in said tray; a vacuum station having a vacuum chamber forenveloping said test card and test sample, said vacuum station having ameans for supplying vacuum to said vacuum chamber and releasing saidvacuum to atmosphere, wherein the release of vacuum thereby causing saidtest sample to enter into said test card via said fluid communicationbetween said test card and said test sample; an incubation stationincubating said test card after said sample has been loaded into saidtest card in said vacuum station; an optical reading station conductingoptical analysis of said sample loaded into said test card; and amovement system moving said test card and test sample from said loadingstation to said incubation station, and moving said test card from saidtray into said incubation station and for moving said test card fromsaid incubation station to said optical reading station.
 2. The machineof claim 1, wherein said vacuum chamber cooperates with said tray toform a vacuum enclosure surrounding said test card enabling said testsample to be loaded into said test card.
 3. The machine of claim 1,wherein said machine further comprises a sealing station for sealingsaid test card after loading of said test card with said test sample. 4.The machine of claim 1, wherein said incubation station comprises arotating carousel containing a plurality of slots, each slot forreceiving a test card, and wherein said carousel is rotated about anaxis in synchronism with the movement of said tray past said incubationstation, whereby said plurality of test cards may be loaded into saidplurality of slots in said carousel as said tray is moved past saidincubation station and said carousel is rotated about said axis.
 5. Themachine of claim 4, wherein said carousel is oriented such that saidcarousel rotates about a horizontal axis.
 6. The machine of claim 1,wherein said optical reading station comprises a transmittance detectionstation.
 7. The machine of claim 6, wherein said optical reading stationfurther comprises a fluorescence detection station.
 8. The machine ofclaim 6, wherein said test card comprises a plurality of wells arrangedin a plurality of columns, wherein said transmittance detection stationcomprises a plurality of detectors arranged in at least one column, andwherein said detectors are operative to read said plurality of columnsof wells in said test card as said test card is moved by said test cardtransport system past said transmittance station.
 9. A microbiologicalsample testing instrument for testing test sample fluids containingmicrobiological samples, said test sample fluids contained inreceptacles, said instrument adapted for use in conjunction with testsample cards having a plurality of sample wells placed in fluidcommunication with said test sample fluids, said test sample cardscomprising susceptibility cards and identification cards, the instrumentcomprising:a tray adapted for holding a plurality of said receptaclesand a plurality of said test sample cards; a vacuum station having avacuum source for loading said plurality of test sample fluids into saidwells of said plurality of test sample cards, said vacuum station havinga vacuum chamber, said vacuum source supplying vacuum to said vacuumchamber and releasing said vacuum to atmosphere, wherein the release ofvacuum thereby causes said test sample fluids to enter into said testsample card via said fluid communication between said test sample cardand said test sample fluids; an incubation station for incubating saidtest sample cards; a system loading said plurality of test sample cardsfrom said tray into said incubation station; a reading system forconducting optical analysis of said wells in said test sample cards; anda movement system for moving said plurality of test sample cards andsaid tray from a loading station to said vacuum station, from saidvacuum station to said system loading said test sample cards into saidincubation station, and for moving said test sample cards from saidincubation station to said reading station.
 10. The instrument of claim9, wherein said instrument further comprises a sealing station forsealing said test sample cards after loading of said test sample cardswith said test sample fluids.
 11. The instrument of claim 9, whereinsaid incubation station comprises a rotating carousel containing aplurality of slots, each slot for receiving a test sample card, andwherein said carousel is rotated about an axis in a predetermined raterelative to the movement of said tray past said incubation station,whereby said plurality of test sample cards may be loaded into saidplurality of slots in said carousel as said tray is moved past saidincubation station and said carousel is rotated about said axis.
 12. Theinstrument of claim 11, wherein said carousel is oriented such that saidcarousel rotates about a horizontal axis.
 13. The instrument of claim 9,wherein said optical reading station comprises a transmittance detectionstation.
 14. The instrument of claim 13, wherein said optical readingstation further comprises a fluorescence detection station.
 15. Theinstrument of claim 13, wherein said sample wells of said test samplecards are arranged in a plurality of columns, wherein said transmittancedetection station comprises a plurality of detectors arranged in atleast one column, and wherein said detectors are operative to read saidplurality of columns of wells in said test card as said test card ismoved by said card transport system past said transmittance station. 16.The instrument of claim 9, wherein said tray holds at least 5 of saidopen receptacles and at least 5 of said test sample cards.
 17. Theinstrument of claim 9, further comprising a bar code reader positionedwithin said machine in a location to read a machine-readable indiciaapplied to surface of said test sample cards.
 18. A unitary sampletesting instrument for testing a sample delivered to a test sample cardhaving a plurality of reagent-filled test sample wells, the instrumentcomprising:a tray adapted for holding a plurality of sample receptaclescontaining samples to be tested and a plurality of said test samplecards, each of said test sample cards placed in fluid communication withone of said plurality of receptacles; a vacuum station having a vacuumchamber moveable with respect to said tray in a manner to form a vacuumenclosure around said plurality of receptacles and said plurality oftest sample cards, said vacuum station further comprising a controllablevacuum source operative to load said plurality of test sample fluidsinto said wells of said plurality of test sample cards; a rotatablecarousel containing a plurality of slots, each slot for receiving one ofsaid test sample cards; a system for moving said tray within saidinstrument from a loading station to said vacuum station and from saidvacuum station to said carousel, said system moving said tray in apredetermined manner relative to the rotation of said carousel andincluding a means for removing said test sample cards from said traysuch that said plurality of test sample cards are individually andautomatically transported out of said tray into said slots of saidcarousel; an optical reading station for reading said wells of said testsample card; and a sample card transport mechanism for moving said testsample cards from said carousel to said optical reading station.
 19. Thesystem of claim 9 wherein said vacuum station cooperates with said trayto form a vacuum enclosure surrounding said test sample card enablingsaid test sample to be loaded into said test sample card.